OK, I'll be the only honest person here. Nobody can explain mileage runs. It's just something people do.

If you want to get from point A to point B, you do so by figuring out the most stops, most miles, or both you can possibly get for that flight. You will see people here posting things like from A to B via C, D, E, F, and G.

Some people aren't doing it for awards, they never spend their miles. Personally, I do it for status, for the shorter lines in the status lines, to get on the plane first, for upgrades to clear earlier, etc.

Minimum per leg - usually, but depends on the airline.

Dangers to aviod - the biggest is your friends and coworkers will think you are nuts for running off to London for a day or two to have a few beers and catch a play or to some city across the country for a day because it's on sale that weekend and you just saw a special on hot dog stands on Food TV and there was one in that city rated number 1.

Besides people thinking you are nuts, no real dangers.